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Lucas123 writes "A solar power array that covers three square miles with 3,200 mirrored parabolic collectors went live this week, creating enough energy to power 70,000 homes in Arizona. The Solana Solar Power Plant, located 70 miles southwest of Phoenix, was built at a cost of $2 billion, and financed in large part by a U.S. Department of Energy loan guarantee. The array is the world's largest parabolic trough plant, meaning it uses parabolic shaped mirrors mounted on moving structures that track the sun and concentrate its heat. A first: a thermal energy storage system at the plant can provide electricity for six hours without the concurrent use of the solar field. Because it can store electricity, the plant can continue to provide power during the night and inclement weather."

Interesting that the wholesale price of this electricity is 14c/kWh. The overnight residential rate in Phoenix is about 7c. I guess they're hoping to resell a lot of this to businesses during the day, or they're just going to eat the price difference (over nuclear, gas and coal) to meet the 15% renewable energy mandate for 2025.

They can sell it to California! I don't think they are building a lot of power plants here, and we'll definitely need some clean environmentally friendly energy to power the high speed train they are going to build. Besides PG&E and SCE get away with charging >.30/kWh to customers, so there is plenty of potential for profit there even at a wholesale cost of.14/kWh.

If you doubt they would do this, consider that California once imported (and may still be importing) clean hydroelectric power from Cana

Unfortunately, the link you posted doesn't mention the timescale for energy generation. I am under the impression that, like nearly all solar energy technology, that the primary cost is up-front installation, and maintenance costs are virtually zero thereafter. Using this assumption, we have

price / kWh = 2 (billion $) / (280 MW * t)

This gives t = (2 billion hours) / (280e3 * [100 * price in cents/kWh]) as the amount of time it would take to break even, or with some simplification, 81.485 years / P where P is the price in cents / kWh at which you wish to sell.

So if you were to sell at $.07 / kWh, it would ideally take 11.64 years to recoup investment (not taking into account additional costs and possible fluctuation in energy output). At double that price, it will take half the time. Either way, after that, I would say it's free energy. I don't see why there aren't more projects like this.

The uninformed who spout off endlessly about how great green energy is rarely realize or talk about the cost to keep the power plants running at peak efficiency for a long enough time to recoup the initial investment. So what are the overhead costs? If they increase the cost of electricity to the consumer, are they going to care that there's a chance the Great Barrier Reef won't shrink as much especially since most of them couldn't afford to go see it?

In 2010 there were 114,800,000 U.S. households, 114,800,000 / 70,000 powered homes = 1,640 of these facilities at 3 square miles per facility = 4,900 square miles! Airizona is 114,006 square miles, that is 4.2% of the state covered in panels....or roughly the entire state of Connecticut if you have some room for growth.

That's why solar arrays should go on the roofs of existing urban buildings -- the ground is already in use (no new ground need be destroyed**) and the power is produced where it's to be used (rather than requiring new transmission lines).

** If you haven't actually seen a desert solar facility -- they produce a scorched-earth effect locally and a heat/dust shadow for several miles downwind. They're extremely destructive of the desert ecology and environment, which is not nearly so lifeless as most 'greenies' and city slickers believe. Would they be so cavalier about it if, say, solar facilities were built in forest or wetlands? Putting 'em in the desert, which has a far harder time recovering from abuse, is elitist NIMBYism.

A loan guarantee is not financing. The DOE has provided no money. The financing is from private institutions.

The loan guarantee means the private institutions get paid even if the project fails, true. But why should the project fail? This is proven tech that's cost competitive. It would take some true catastrophe for the loan guarantee to ever be called on.

I'm not saying it's useless, but I am curious if there's some fundamental limitation that's caused this. If you want base load power, you'd probably want more like 12 hours of storage and it seems strange they wouldn't go for that, since they're half way there. If you're only going for intermittent power, this system is more expensive to build and operate than a photovoltaic system would be, but it makes sense if you add energy storage to the picture.

Few people here turn their cooling systems OFF during the day. Also, the hottest days of the year here are in the summer, where a lot of families have kids at home. YES, there's absolutely a spike in electricity around 4pm (when it's still hot and people come home), but businesses (which a lot of us go to during the day) have air conditioners too.

Most of you don't work weekends, and probably half the homes have somebody home during weekdays (retired people, unemployed people, stay at home parents, latch key kids), and it's hotter during the day than the evening, so you need a lot of daytime power still.

Yes, but during our horrible, soul-killing abominable summers (6 months out of the year) AC usage 24/7 is pretty well required. How many nights a year does the overnight low not dip below 100?
(I moved to phoenix from oregon, i might be.. exaggerating, but shit summers be hot here.)

Economics. You don't need nearly as much power between midnight and 6 (7? 8?), during which time the nukes and coal, which can't be throttled too much, will oblige. Designing heat storage capacity for around-the-clock is wasting money, at least in the current grid configuration and state of the tech.

If you want base load power, you'd probably want more like 12 hours of storage and it seems strange they wouldn't go for that, since they're half way there.

You can trade peak power for more hours of lesser power generation, but it's not a balanced 1:1 trade off.For every extra hour of heat retention, you lose a lot of your power generation.And it's also more expensive to operate that type of plant.

Base load is the easy stuff in power generation. The peaks are vastly greater than the minimum demand at night.

this system is more expensive to build and operate than a photovoltaic system would be

Not at large scales. PV does not scale well since if you double the size you only double the output. With thermal solutions of all types you can get a lot more heat out of stuff if you have a lot of hot stuff, so doubling the size gives you more than double the output due to an increase in the amount of energy you can get out. For example, if you don't have much steam you can only have a high pressure turbine but if you have a lot you can use the leftover steam that comes out of the first turbine and feed it into another with a different blade pattern to extract more energy and so on.With thermal it has to be big so you have an enormous capital cost, but if it's big enough PV just will not match it. A 500MW PV array would cost a vast amount more than a 500MW thermal solution.

However the amount of electricity produced is not. You can recover energy more energy from a vast amount of steam pushing a series of turbines around to drive generators than you could from the electrons coming from the PV cells coving the same area.

Make it bigger and those costs come down. Of course the sensible thing is to solve a lot of problems by building a pilot plant such as this before you build the large plant - hence this project. It's not big but it's big enough for a proof of concept.So in other words this thing makes perfect sense and bitching about it is like complaining that the Wright brothers didn't start off with a SR71. Why should they have bothered when airships existed?

I'm not saying it's useless, but I am curious if there's some fundamental limitation that's caused this. If you want base load power, you'd probably want more like 12 hours of storage and it seems strange they wouldn't go for that, since they're half way there. If you're only going for intermittent power, this system is more expensive to build and operate than a photovoltaic system would be, but it makes sense if you add energy storage to the picture.

Or more likely, they did some demand modeling and found some value that made the economic sense?

Electricity demand follows a predictable pattern, with the lowest demand between 10pm and 7am. If surplus power (to storage) were to transition from positive to negative in the early evening, then 6 hours of stored capacity might work out pretty well.

Yes, night is longer than the 6 hours mentioned in the story summary. But the story summary is a bit misleading.

That is six hours running at full capacity and also running entirely from the salt tanks. Neither of those conditions are likely to be true overnight.

Solar plants continue operating at reduced power during cloud cover and at night time. Even at times of reduced sunlight or at night there is still energy available. It does not need to run entirely from the salt tanks.

Secondly, nighttime is not peak usage hours.

The Solana salt tanks are about 740 cubic meters so they could probably store around 16TJ of energy. (For physics impaired, 1 joule per second == 1 watt.) That is a lot of power. Since it will mostly be relying on that stored energy at night and not running at full capacity, that stored energy could reasonably last through the night and on through a good portion of the following day.

Technically nothing stores electricity except for super-cooled superconductors. Batteries "store electricity" in the form of chemical energy and even capacitors only "store electricity" as two charged plates. But I think we all know what they meant, that it was storing the potential for electricity.

Actually, when you read up on it, the storage capacity is exhausted shortly after sunset. 6 Hours max.The efficiency falls off at low sun angles.

Sunset usually happens right at peak demand time, evening cooking, and late afternoon air conditioning.Plus the site has high ground to the immediate west, sunset comes earlier for them.

Don't get me wrong, this is an impressive feat of engineering.

It was installed very fast, hacked out of prime farm land (or as prime as it gets in Arizona).Google Maps Satellite view, with imagery dated 2013 http://goo.gl/maps/Qh7e5 [goo.gl] shows nothingbut desert with truck roads laid out, and now they are up and running.

(Either that or Google is Playing Fast and Loose with image dates, because Google Earth shows the sameimages but has a 2010 date on them)

The efficiency falls off at low sun angles.It falls off faster for solar hotwater (like this plant) than for photo-voltaic.You start drawing on your stored heat WELL BEFORE sunset, usually severalhours before sunset, because as I pointed out that is the peak demand period, and yourstorage is exhausted in 6 hours, from the time you start drawing.

So maybe two or three hours after sunset your storage is exhausted.Its a long time till sunrise.

Except the collectors, although not operating at peak efficiency, due to the sun light passing through more air (but the effective surface area is still the same, since the mirrors rotate to track the sun) they still provide heat energy to the molten salt, right up until sunset.

You never build a Solar plant because you need more electricity. Because if you build one you also have to build a traditional plant in order for cloudy days and night

Except for the fact that, in the southwestern US, peak power demand tracks sunlight pretty well. And that peaking plants (run on coal) are fairly expensive. And that all that solar power can simply displace daytime use of hydro, which can fill-in the shortfall on cloudy days of high demand.

What I don't get is why they only went for six hours of storage capacity? A few years ago, a friend of mine described an idea to me for a salt tank system that would take days to come up to working temperature, and days to cool off. You'd just add heat whenever you could, and draw power whenever you needed it. His estimate was that the power would end up costing 3 to 4 cents per KwH.

More storage capacity beyond peak hours probably isn't profitable. You want to sell electricity during peak because that's when you're getting the highest dollar value for your power. They probably designed the salt storage, so the total output of the plant was extended long enough to generate during those peak evening hours, and no longer, so baseload power takes over. The smaller your storage is, the less power you would put into storage and the more power you put into spinning your turbine.

it also seems stupid to use a turbine that requires water in the middle of a desert and is subject to the energy lost in conversion. I'm a fan of the "by all means necessary" approach to solving our energy problems but this is just a huge waste IMO. Perhaps it has use as a prototype, otherwise I'm not convinced it's a good idea, at all.

Can you think of another way of generating electricity from heat on a commercial scale?

So I'm not going to respond to the first post because it makes no sense. But I'll happily use the "first reply" spot, thank you very much, to actually say something.
This $2 billion plant breaks down to close to $30,000 per home serviced. Seems a wee bit excessive, considering the average home electric bill in Arizona runs something like $200 (I researched the web for a few minutes to estimate this).
Consider that installing a home solar system would run something like $10-$20k at most in a sunny place like Arizona (considerably less w various tax incentives).
Looking like a bit of a boondoggle?

So I'm not going to respond to the first post because it makes no sense. But I'll happily use the "first reply" spot, thank you very much, to actually say something.

This $2 billion plant breaks down to close to $30,000 per home serviced. Seems a wee bit exc essive, considering the average home electric bill in Arizona runs something like $200 (I researched the web for a few minutes to estimate this).

Consider that installing a home solar system would run something like $10-$20k at most in a sunny place like Arizona (considerably less w various tax incentives).

Looking like a bit of a boondoggle?

This is not how investment in technology works. Solar thermal is still moving down the cost curve and hasn't been deployed to nearly the scale of rooftop PV, but has the potential to massively undercut (at the utility scale, with thermal storage). These investments help the technology reach that point.

Do you have a citation for this? It was my understanding that solar-thermal has not been getting much cheaper, and, unlike solar PV, there is little room for technological improvements (it is basically just a bunch of mirrors). For this reason, most solar-thermal projects around the world have been cancelled and replaced with cheaper PV. Of course, the US government has protective tariffs in place to artificially raise the price of solar-PV. This solar-thermal plant would likely be even more of a loser

PV is only cheaper per watt over lifetime at small sizes. There is a crossover point where thermal solutions make more sense. With PV when you double the scale you get double the output. With thermal you get more than double the output when you double the scale.PV is popular because it can be done at small scales and has been in continuous use since the 1970s. Solar thermal requires great big turbines etc, so a large capital cost, before you can get one watt out of the things so it is very unpopular with those who don't wish to invest (just about everyone in charge of budgets).

I wonder how this compares to the Austin solar plant, which generates a lot less energy than this one (30MW), but it consists of panels on single axis trackers. It cost $250 million, but from what I gather, it should have a long lifespan due to its relative simplicity. Of course, the ability to store energy at night is a big difference, but I wonder which plant will amortize better over time.

Since it's a lot like a coal fired power station without all that corrosive and abrasive coal I expect it will last many decades (just like the coal fired power stations). Steam is fairly well understood even at the low pressure/large turbine end where this is going to be.To put things in perspective with the 30MW plant, you can get 20MW generator sets built in the 1960s that use a single jet engine to drive them. Of course they go through fuel like anything and have serious running costs so I'm only making the comparison in terms of size - even 1970s solar PV would be cheaper over time than those things.

You don't actually have enough information to say. Do the home systems provide electricity after the sun goes down? What is the efficiency after 10 years? What is the expected lifetime of the home systems? What is the expected lifetime of the power plant? How do the costs compare to a conventional power plant? What are the pollution costs? How does it affect the wildlife around the plant? How does that compare to a conventional plant?

This plant cost $7100/kW. For comparison, the US Energy Information Administration estimates a new nuke plant would cost about $5300/kW (and in China, where they actually building many nukes, they're $2000/kW).

Presumably if more of these solar plants were built the cost would come down.

Can that one awesome nuke plant handle the middle-of-the-night baseline loads by itself? If so, fantastic combination with the solar.

At least in summer, Arizona and California need lots of power when the sun is shining, and not nearly as much in the middle of the night. Solar can't provide all energy needs but Arizona is a great place to build a lot of it.

News just in - big stuff costs a lot, big stuff that is a cutting edge experiment even more so.Also I suggest you look at the fine print and breakdown of those numbers you've quoted - I'd say they are assuming the tenth plant or so of a type where savings can be made due to already sunk expenses and from experience. For the China number I suggest you use a real plant instead of a wild estimate. They some AP1000s almost ready to go, a couple of years behind the initial plan and a few billion over expected

Solar home for 20K per house? Closer to 30K, and only if your house happens to be conveniently situated.

You can get in for $5000, if all you want to heat is the pool or maybe some hot water.

Most of the figures you see for solar home additions are for auxiliary heat (usually for hot water), theymake no attempt to cover a house's whole electrical load. With air conditioning, that load can bepretty high, and you never get off the grid.

There are a couple articles on this recently on AZ Central.http://www.azce [azcentral.com]

Spain spent billions on green subsidies, and is on the verge of bankruptcy. As it turns out, Europe has now spent billions on Spain's green subsidies, and Spain's green economy is going bankrupt. Those billions would be kind of useful now, wouldn't they?

Is there any solar power that is not a blight on the land? Nothing quite like enhancing the scenery with 20 huge panels at roadside.

No matter what the power plant... No matter how clean and low-impact it is, some moron ALWAYS has to find something stupid to bitch about.

Are you suggesting that a nuclear power plant would be a scenic tourist attraction, right at home inside Yellowstone? How about a coal power plant, along with the huge open-pit mine where the coal comes from? Or maybe some nice tar sands right outside your back yard?

If you don't like the fact that electricity generation is going to use some land, then cut the power lines coming into your house and live in the nice, scenic, non-blighted dark and cold.

With HVDC transmission lines getting put in that makes a lot of places close enough to get electricity from hydro, or solar from the Sahara or whatever.Remote power sources such as tidal hydro or cold coastal currents near hot land (Atacama Desert) become more viable as transmission losses drop. Even without room temperature superconductors we are headed that way.

According to this [seattle.gov] it is a bit lower than that at about 94.2%. It is also a bit skewed by the fact that Seattle is close to mountain ranges with lots of valleys that can produce hydroelectric power. If you remove the hydroelectric, 89.8% the percentage drops to 4.4%.

Not everyone lives in an area that has plentiful hydroelectric generation. It is like Arizona touting how much solar based electricity they are generating and slagging Seattle for falling behind.

Meanwhile, I just shelled out $150 to buy one unit of the Seattle Aquarium solar panel array, which will reduce my annual already green electric bill by about $46 until around 2035.

That is only because you are getting credited for $1.15/KWh [slashdot.org] when electricity sells locally for $0,0672. You are being paid over 17 times the going rate. Making money due to tax incentives really skews the picture.By the way according to Seattle Power [seattle.gov] the credits amount to "an estimated annual credit of almost $29 per solar unit"I really don't think comparing a highly subsidizes small , 49 kW, project with al large commercial project is very valid at all.

Unless there are some nuclear reactions going on in there, I really don't think it is creating any energy at all, much less "creating enough energy to power 70,000 homes".

Solar energy converts energy from the nuclear reactions in the sun into electricity. Ok, conversion.

Hydroelectric - captures energy stored from gravitational potential energy and converts it using a turbine into electricity. Fine, conversion again.

Coal/Nat. Gas - takes stored energy in the form of deposits of oil, coal and natural gas and uses them to drive turbines... oh, you get the picture. Check, conversion of energy again.

Clearly nuclear energy reactions "create energy" - no wait, it's converting stored energy in the form of nuclear bonds into radiation, which can then be captured as a heat energy which can then drive a steam turbine turning into electricity.... uh... huh.

Conversion is all we can do apparently. We might want to thank/curse this lousy law [1].... who's with me for repeal?!?